Largest known prime number discovered with over 23 million digits

Prime numbers are divisible only by themselves and one, and the search for ever-larger primes has long occupied maths enthusiasts. However, the search requires complicated computer software and collaboration as the numbers get increasingly hard to find.

The new number is as big as 2 raised to the power 77,232,917 minus 1. A number with 23,249,425 digits, given the name M77232917 for short. It is part of the Great Internet Mersenne Prime Search (GIMPS), a project started in 1996 to hunt for these massive numbers. Mersenne primes – named after the 17th century French monk Marin Mersenne who studied them – are calculated by multiplying together many twos and then subtracting one.

The new number was found by Jonathan Pace, an electrical engineer from Tennessee who has been searching for big primes for 14 years. The number is the 50th Mersenne prime to be discovered, and the 16th to be discovered by the GIMPS project. Pace did his calculating work on a pc with a Intel i5-6600-processor (not the latest), and it took six full days. The new prime is verified using four different computer programs on four different computers. It is nearly one million digits longer than the previous record holder, which was identified as part of the same project at the beginning of 2016.
M77232917 is as large as 9,000 printed book pages. You can download this number from the article on the GIMPS project.

The GIMPS project is done by thousands of volunteers sifting through millions of non-prime candidates before the lucky individual chances upon their target. Besides the thrill of discovery, Mr Pace will receive a $3,000 (about € 2500) GIMPS research discovery award.The next Mersenne prime discovery could be smaller or larger than the existing record holder, but the big target for the GIMPS team is to find a 100 million digit prime number.The person who discovers such a number will be awarded $150,000 (about € 125000).